Superoxide dismutases are essential for aerobic life. Iron- and manganese-dependent enzymes share a common protein structure, however they exhibit metal-ion specificity linked to the extended protein environment. Several residues, including Q143 and H30, are important in making indirect interactions with the active-site metal of the human manganese dependent enzyme. High resolution structures of the Q143R, Q143A, H30Q, and H30V mutants, not attainable at our in-house source, will give insight into the physical interactions that tune the redox potential of the enzyme and confer metal-ion specificity on the enzyme.